Our invention relates generally to the formatting or initialization (i.e. writing of track format data preparatory to use) of magnetic disks such as those commonly known as floppy disks. More specifically, our invention pertains to a method of, and apparatus for, formatting magnetic disks of relatively large data storage capacity (high bit density) with use of host equipment that has been programmed for formatting magnetic disks of smaller capacity.
Floppy disks are now commercially offered in various sizes, with different storage capacities and track formats. They are mounted in floppy disk drives (FDDs) of matching constructions and operating speeds for the transfer of data therewith. Normally, to make up a self contained data processing system, a required number of such FDDs are daisy chained to an FDD controller which in turn is coupled to a central processor unit (CPU). The FDD controller and CPU constitute, in combination, host equipment to which the FDDs are subordinate, the transfer of data to and from the floppy disks in the FDDs being effected under the control of the host equipment. FDD controllers are available on the market in the form of large scale integrated (LSI) circuits chips, examples being those trademarked "FD 1791" and a related series of products manufactured by Western Digital Corp., and ".mu.PD 765" manufactured by Nippon Electric Corp.
As is well known, each floppy disk just purchased and loaded in the matching FDD must be formatted or initialized preparatory to the commencement of normal data transfer operation. Usually, the host equipment is programmed to format floppy disks of only the particular data capacity intended for use with the FDDs under the control of the host equipment.
Take, for example, floppy disks having a standard format of 16 sectors per track, and those having another standard format of 32 sectors per track. The data storage capacity of the former is half that of the latter. We will call the floppy disks of the first mentioned and comparable formats the small (or smaller) capacity floppy (or magnetic) disks, and those of the second recited and comparable formats the large (or larger) capacity floppy (or magnetic) disks. The small capacity floppy disks are intended for use with matching small capacity FDDs (SCFDDs), and the large capacity floppy disks for use with matching large capacity FDDs (LCFDDs). The LCFDDs operate at a data transfer speed twice that of the SCFDDs as the bit density of the large capacity floppy disks is twice that of the small capacity floppy disks.
Heretofore, the formatting of the small and large capacity floppy disks has required host equipment programmed exclusively for either type of record media. FDD controllers programmed for small capacity floppy disks are now available at reduced costs because of the more widespread acceptance of such small capacity floppy disks and associated SCFDDs. As far as we know, however, the low cost FDD controllers programmed for small capacity floppy disks have heretofore been incompatible with LCFDDs by reason of the difference in format between the small and large capacity floppy disks. In the light of the definite advantage of greater storage capacity possessed by large capacity floppy disks, we believe that this seeming incompatibility must be overcome in order to make them, together with the associated LCFDDs, more readily acceptable to prospective users.